OPTICAL-PROPERTIES OF SI CLUSTERS AND SI NANOCRYSTALLITES IN HIGH-TEMPERATURE ANNEALED SIOX FILMS

Structure, optical absorption and photoluminescence (PL) properties of SiOx films subjected to thermal annealing at 750-1100 degrees C are i nvestigated. Si crystallites with a few nanometers in size are observe d in the SiO1.3 and SiO1.65 films annealed at 1100 degrees C. Threshol d energies in optical absorption of the Si nanocrystallites are higher than that for bulk Si, suggesting a contribution from quantum confine ment effects. The PL spectrum shows a remarkable increase in intensity after annealing at temperatures above 1000 degrees C. This PL behavio r is closely related to the formation of Si nanocrystallites by the an nealing. The PL peak energy of the annealed films shifts to higher ene rgy with decreasing crystallite size but does not follow the blueshift for the absorption threshold energy. These results suggest that a loc alized state contributes to the PL mechanism. The SiO1.8 film annealed at 1100 degrees C, which contains no Si crystallites, exhibits an int ense pi, similar to the annealed SiO1.3 and SiO1.65 films. It is impli ed that noncrystalline Si nanoparticles are formed in the SiO1.8 film under high-temperature annealing. (C) 1998 American Institute of Physi cs.